1. Field of the Invention
The present invention relates to a pad area and a method of fabricating the same. More particularly, the present invention relates to a pad area and a method of fabricating the same that are capable of improving contact characteristics of an interconnection layer and a conductive ball by additionally forming an embossed layer having a plurality of embossed patterns under the interconnection layer of the pad area to form embossments on the interconnection layer, or reducing a step difference between the interconnection layer and a passivation layer to minimize a contact error by additionally forming an embossed layer having a single embossed pattern in a multi-layer structure of a semiconductor layer, a gate insulating layer, a gate electrode, and so on.
2. Description of the Related Art
Recently, in order to solve problems related to conventional cathode ray tube (CRT) displays, including weight and bulk, attention has turned to flat panel displays such as, e.g., liquid crystal display (LCD) devices, organic light emitting display (OLED) devices, field emission display (FED) devices and plasma display panel (PDP) devices.
LCD devices are capable of exhibiting good resolution, good color reproduction, good image quality, with low power consumption, in comparison with other flat panel displays. OLED devices are capable of having a simple structure, high optical efficiency, low voltage, direct current driving capability, and rapid signal response speed due to emissive characteristics of organic materials. FED devices are capable of exhibiting high resolution and wide viewing angles. PDP devices are capable of exhibiting high brightness, high emission efficiency, and wide viewing angles.
A flat panel display may be fabricated by forming devices on a transparent insulating substrate such as a glass or plastic substrate.
In order to operate a flat panel display, components for generating various control signals or data signals may be mounted on a predetermined region of the substrate on which the flat panel display is formed. Depending on the method used in mounting the components on the substrate, a flat panel display may be classified as a chip on glass (COG) type or a chip on flexible printed circuit (FPC) (COF) type. In a COG type flat panel display, components, e.g., integrated circuits (ICs), may be directly mounted on the substrate. In a COF type flat panel display, components, e.g., ICs, may be formed on a film (e.g., polyimide film), and the film having the components are then mounted on the substrate.
In both COG and COF type flat panel displays, a conductive pad is needed to properly mount the components on the substrate. In addition, an anisotropic conductive film (ACF) may be used between the conductive pad and the components, and an ACF ball may be disposed in the ACF to electrically connect the conductive pad and the components.
In conventional conductive pad structures, however, contact errors may result when components are mounted due to a step difference between a passivation layer surrounding an edge of the conductive pad and an interconnection of the pad, and improper contact caused by a small contact area of the ACF ball. Such contact errors may cause improper operation of the flat panel display and result in defective devices.